Literaturdatenbank
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Allman, P. E. (2006). Consequences of egg size on hatchling energetics in the diamondback terrapin, malaclemys terrapin: a geographic comparison. Unpublished thesis Doctor of Philosophy (PhD), Ohio University.
Added by: Admin (14 Aug 2008 20:33:41 UTC) |
| Resource type: Thesis/Dissertation BibTeX citation key: Allman2006 View all bibliographic details  |
Categories: General Keywords: Emydidae, Fortpflanzung = reproduction, Habitat = habitat, Malaclemys, Malaclemys terrapin, Nordamerika = North America, Schildkröten = turtles + tortoises Creators: Allman Publisher: Ohio University |
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| Abstract |
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Organisms typically show phenotypic variation across environmental conditions, and in wide-ranging species, this variation is often explained through local adaptation theory. Whether the differences result from evolution or individual plasticity, the variation is often hypothesized to increase the fitness of individuals in that environment. Egg size in oviparous reptiles often varies among populations and can significantly influence key life history traits such as offspring size, growth, sex, survivorship, and ultimately individual fitness. Therefore, understanding the evolution of egg size and clutch size among populations of a single species is central to life history theory. This dissertation examines the energetic consequences of egg size among three populations of the diamondback terrapin, Malaclemys terrapin, along a latitudinal gradient. The primary goal was to identify the physiological mechanisms that explain the significance of egg size variation in this long-lived ectotherm. Specifically, I asked the following questions: 1) Does the quantity or component proportions of energetic lipids in the egg yolk vary among populations, 2) What are the consequences of incubation temperature and egg size on hatchling size, growth, energetics, and survivorship when raised in different conditions, and 3) What is the rate at which hatchling turtles utilize residual energy stores for six months after hatching. Female terrapins in northern populations lay relatively small eggs in large clutches whereas, in southern populations, they deposit larger eggs in small clutches. The larger eggs from southern populations have a higher proportion of energetic lipid stores, and under similar incubation conditions, these eggs produce larger hatchings with a higher proportion of residual energy stores. However, these hatchlings also have a higher maintenance metabolism and utilize the energy stores at a faster rate. In warmer climate conditions, the larger turtles grow faster than smaller turtles with less residual yolk. Additionally, these larger turtles have a higher survivorship. Consequently, I suggest females that deposit larger eggs in southern climates are favored through increased survivorship afforded to the offspring, whereas females that deposit small eggs in northern populations are favored through selection on fecundity.
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